Oxidation Number Lesson Plan
Emily Qu =D
Duration Activity Plan
5 min
Review
1. What do you remember about atomic numbers? (# of positive
charge)
2. If we know the number of proton an atom has, what can we predict
about the number of electrons? Why are the equal? (Achieve
Stability)
3. Every atom of every element has e- arranged in energy levels.
Energy levels corresponds to the period or row that the element is
located (ex. Na in alkali metal, 3rd row-> electrons are located in 3
energy levels)
4. Draw energy level diagram for sodium. Atomic number is 11-> 11
proton and electron
-draw 3 circles around Na nucleus
-on inner circle, max of 2 e-on the next circle, max of 8 e-So far we have 10 e-, we have 11 in total
-for a chemical reaction to occur, energy level must be completely
full or empty, must give up 1e- or gain 7e- for a successful reaction
-compare # of proton and electron, uneven, this is the oxidation
number
5. If class is confused, go over ON for Li. Discuss similarities
between Na and Li
15 min
Lesson
Hand Out Work Sheet (Attached)
1. The Elements: The oxidation number of a pure element is zero
e.g. Fluorine in F2 has ON of 0
2. Simple Ion Charge = Oxidation Number
e.g. Na1+ has ON +1, Mg2+ has ON +2
3. Hydrogen: Hydrogen has ON +1 in all
compounds except in metal hydrides where
it is -1.
e.g. Water: H is bonded to O by a
polar covalent bond. The e- pair is
closer to O -> H is partially positive
(δ+) and O is partially negative (δ-). H
has ON of -1.
4. Oxygen
O usually has ON of -2, except in peroxides where it is assigned -1,
and in OF2 where it is assigned a +2 due to the higher
electronegativity of F.
-In calcium oxide, CaO, oxide ion has a 2- charge. Its oxidation
number is -2
-In H2O2, Each O is assigned the ON of -1
15min
Group
Divide the class up into group of 4. Each group has to come up with 8
Activity different ions. Each ion has to correspond to a different ON ranging from 3 to +3 with no repeats. Students then have to pair up their elements to
15min
Lesson
Cont.
form compounds.(for example, Na+ is +1, Cl- is -1, they can be paired
together. Mg2+ is +2, O2- is -2, and they can be paired together). Take up
answer in class.
5. Covalent Compounds: In compounds that do not contain hydrogen
or oxygen, the more electronegative element is assigned the
oxidation number it would have in an ionic compound. (Provide
electronegativity table)
e.g. In SCl2, chlorine has a higher electronegativity so it is
assigned -1 first and sulfur is assigned +2.
6. Compounds: The sum of the ON in a compound is zero.
e.g. The sum of ON in NaCl is (+1) + (-1) = 0
7. Polyatomic Ions
The sum of the oxidation numbers of the elements in a polyatomic ion
must equal the ion charge. Consider these examples.
e.g. Carbonate ion,
. O has ON of -2. There are 3O in the
formula so the total negative charge is 6-. Since the carbonate ion
has a charge of 2-, the ON of C must be +4.
20min
(if time
allows)
Game
Bingo game:
Give each student a different bingo sheet. They will have to calculate ON
of certain ions or molecules in a compound from the questions given (try to
pick your questions out of a hat so it looks fair). Students then circle the
corresponding ON on their bingo sheet. The first student to get a row, a
column, or a diagonal line wins
Bingo sheet example:
+1 +5 -2 +2
+7 -1 0 +6
0 +2 -1 -2
+4 +1 -3 +3
Questions:
- elements not combined with others? (0)
- oxygen in compounds (-2)
- A metal which has lost 4 electrons (+4)
- Iron in the compound Iron (III) oxide (+3)
- Cl in Cl- (-1)
- Mn n MnO4-(+7)
- S in SO42- (+6)
- N in NO3- (+5)
- Nitrogen in ammonia (-3)
- Chlorine in ClO3- (+5)
- Cu in Cu2+ (+2)
- Na in Na+ (+1)
Take up answers
Note:
ON=oxidation number
e- = electron